Over the recent years, with higher performance of electronic devices, or with the rapid spread of portable devices, electronic parts are requested to have an improvement of high frequency characteristics together with high-density packaging. What is examined to respond such a request is a manufacturing method capable of attaining a hyperfine element or high-accuracy manufacturing in the process of producing the electronic parts. Documents disclosing these methods are given such as Japanese Patent Application Laid-Open No. 2001-85264, Japanese Patent Application Laid-Open No. 2001-110662, Japanese Patent Application Laid-Open No. 2001-76959, Japanese Patent Application Laid-Open No. 2000-331858, Japanese Patent Application Laid-Open No. 2000-331865, Japanese Patent Application Laid-Open No. 2001-111223, Japanese Patent Application Laid-Open No. 2000-183530, and Japanese Patent Application Laid-Open No. 10-12455.
For instance, the manufacturing method will be briefly described by exemplifying a so-called laminated ceramic inductor as the electronic part. To begin with, a slurry obtained by mixing ceramic powder exhibiting a predetermined electrical characteristic with an organic binder is coated thick over a support body such as a PET film. On the thus-acquired insulator layer, metal paste composed of the metal powder and the organic binder is further printed in a predetermined pattern, thus forming an electrode layer. This electrode layer configures part of the inductor body of the ceramic inductor.
A sheet including the inductor of which part is formed on the thus-acquired insulator and a sheet composed of only the insulator are laminated. On this occasion, respective electrode layers on the individual sheets are electrically connected through conductive portions (posts) provided inside the insulator sheets, thereby forming a laminated body serving as the ceramic inductor body. After forming the laminated body, the laminated ceramic inductor is acquired by further executing processes such as sintering and forming an end face electrode. The method of manufacturing the laminated type electronic part etc. other than the ceramic inductor also basically involves conducting a step pursuant to the aforementioned manufacturing step.
In the aforementioned manufacturing method, however, there occurs a limit to providing the electronic part having the higher performance due to scatters in shape and thickness of each layer, a scatter in shrinkage ratio when sintering, etc. Such being the case, the present applicant proposes the electronic part manufacturing method as disclosed in Japanese Patent Application Laid-Open No. 2001-85264 or Japanese Patent Application Laid-Open No. 2001-110662 given above, thus trying to correspond to the high performance requested of the electronic part.
For example, Japanese Patent Application Laid-Open No. 2001-85264 discloses a method of manufacturing the so-called laminated ceramic capacitor as one of the electronic parts. In this manufacturing method, specifically, to start with, a photosensitive slurry obtained by mixing the organic binder exhibiting photosensitivity and the ceramic powder is coated to a predetermined thickness over the surface of the support body subjected to a conductive process beforehand. It is to be noted that this photosensitive slurry may also be formed by an electro-depositing technology. Subsequently, the photosensitive slurry undergoes an exposure process based on ultraviolet rays via a photomask and a developing process using a developer, whereby a layer constructed of a spatial portion and a ceramic portion is formed on the support body.
Herein, an eutectoid layer composed of Ni powder and an acrylic resin is deposited by the electro-depositing technology on this spatial portion to a thickness that is substantially the same as a thickness of the ceramic portion. The thus-acquired sheet constructed of the ceramic portion and the eutectoid layer portion containing the Ni powder is exfoliated from the support body as an integral body and is subjected to the processes such as laminating, sintering and forming the end face electrode, thereby obtaining the laminated ceramic capacitor. Further, Japanese Patent Laid-Open No. 2001-110662 discloses a method of forming the so-called laminated ceramic inductor, wherein this manufacturing method deals with forming the ceramic portion and the spatial portion on the support body, forming the eutectoid layer containing Ag powder over the spatial portion, and so on.
According to the electronic part manufacturing method disclosed in Japanese Patent Application Laid-Open No. 2001-85264 or Japanese Patent Application Laid-Open No. 2001-110662 given above, there is no difference in layer thickness between the ceramic portion and the eutectoid layer in the sheet itself formed on the support body, i.e., these thicknesses are substantially uniform. Hence, as compared with the conventional method of laminating the simple ceramic pattern and the simple electrode pattern, there is a small change in the electrical characteristic due to the sintering process etc., and it follows that the electronic part exhibiting a desired electrical characteristic is obtained with high reproducibility.
At the present, a frequency of a signal used for the electronic device etc. becomes as high as a GHz band, and, for gaining flexibility to the rise in frequency, much higher performance such as decreasing capacitance of a transmission line and reducing resistance at a joining portion is also desired of the above-described electronic part etc. At the same time, further high integration and further downsizing are desired for being provided to the portable terminals. As for the sheet obtained by the aforementioned manufacturing method, it is considered that, for instance, the flexibility to some extent can be attained by making advance in parallel with thinning the layer and optimizing the material such as the conductive paste.
The sheet acquired by the manufacturing method described above is, however, merely made from the two types of materials, i.e., the ceramic portion and the eutectoid layer portion. Accordingly, a restriction that the single sheet be constructed of the single type of insulator and the single type of conductor, is always imposed in terms of manufacturing the electronic part. As a result, it is considered that there might be incurred situations such as 1) causing a restriction in the circuit design and hindering the high integration from a certain level, 2) extremely increasing the number of layers to be laminated and hindering the downsizing from a certain level in the case of forming the electronic part including, e.g., the inductor, and 3) causing a possibility that the reliability decreases due to an increase in the number of layer-to-layer connecting portions as the number of layers increases.
Moreover, the photosensitive slurry is, as explained earlier, acquired by mixing the organic binder having the photosensitivity with the ceramic powder. The ceramic powder normally has an effect of diffusing the ultraviolet rays when in exposure. Therefore, there occurs a phenomenon such as blurring in pattern edge when exposed. As a consequence, in the prior art, when a ratio of a thickness to a width of the wiring pattern to be formed is set as an aspect ratio (thickness÷width), its upper limit is approximately 0.5 through 0.67.
Japanese Patent Application Laid-Open No. 2001-110662 discloses a method for corresponding to this condition. To be specific, a layer composed of only a negative resist formed on a base (substrate) is subjected to patterning, a ceramic portion is formed in a space formed after the patterning by employing the electro-depositing technology, a resist-layer undergoing the patterning is removed, and a portion exhibiting conductivity is formed by the electro-depositing technology in a spatial portion formed after the removal.
According to this method, none of the blur occurs at the pattern edge described above, and hence the sheet having high pattern accuracy can be formed. The restriction that the single sheet be constructed of the single type of insulator and the single type of conductor is, however, still always imposed on even this method. Accordingly, a probability that the situations given in the items 1) through 3) described above is, it is considered, the same with this method.